Maple tree leaves dying

Asked September 5, 2020, 1:11 PM EDT

Our maple tree has multiple small branches with dying leaves. Also the tree has variegated leaves on the lower branches and solid green leaves on the upper levels. are these signs of a disease/infestation?

Multnomah County Oregon

3 Responses

While I am unfamiliar with the weather conditions in your area which would preclude this diagnosis, this could be a sign of Verticilium Wilt. Prune out one of the affected branches and slice it on an angle. If you see a blackened ring on the end cut or dark streaking inside the stem then odds are very good that is the issue. Unfortunately the only treatment is helping three combat this soil borne pathogen on it's own. It is however important to get it properly diagnosed as it can be deadly to a new tree planted to replace this one later on.

What to do now:
  1. Prune out affected branches.
  2. Make sure the tree is protected from moisture stress by adding a layer of mulch around it that is 2-3 inches deep. You MUST leave at least six inches from the trunk bare to protect the bark from rodents and other pathogens.
  3. Deep water using a 5 gallon bucket with small holes in the bottom during periods of drought.
  4. Be very careful in the root zone of this tree so to prevent further damage (this means no planting in this area)!
Finally, how long ago was that driveway poured? Often root damage due to these types of construction projects don't show up for 5-10 years. The driveway is very close to the tree and significant damage to the root system may have occured. You will need to take great care to help regenerate the roots and may need to fertilize the tree to assist. Watering will also be crucial if this is the case as the tree would have less roots to find and absorb water. Continue to water at least once a month (depending on rainfall) until the ground freezes. Roots continue to grow even after the leaves fall.

I'm adding my opinion for several reasons. First, because I was originally assigned to respond to your inquiry, second, because I live near you and am very aware of current conditions in this part of the northwest.

For the past 6 or so years, our region has endured a continuing drought along with elevated temperatures. This year has been a particularly bad year, especially for native plants and those that don't receive supplemental water, whether they're in wild sites or landscape.

Even though maples are very susceptible to Verticillium Wilt, a serous soil-borne disease, it's very likely that your maple is short of water. Beyond the continuing drought, I see that the tree also receives reflected light and heat from the nearby concrete surface.

To help evaluate the soil's moisture condition, please respond to the following questions:
- How often do you water this tree?
- What sort of irrigation system do you use - hand-held hose; sprinkler (oscillating or in-ground); drip line; or soaker hose?
- How long do you run the system each time?
- How often do you water?

Consider ignoring the suggestion to water the tree with a 5-gallon bucket. The roots of this established tree extend far into the adjacent planting bed, out of reach of a bucket.

Okay, let's switch to a different subject.
If you haven't yet cut off the branches with dry leaves, consider waiting until spring. The tree will "tell" you what is dead and what is alive. Then, after new growth is well underway, cut off the dead wood.

Also consider adding a 3-inch deep mulch of wood chips on the bare soil under the tree. Doing so will help slow evaporation from the soil.
The questions in the previous response about the driveway installation versus the tree's roots may also be also be provides insights as to why the tree has problems. Basically, which came first -- the tree or the driveway?

I look forward to receiving your responses about supplemental irrigation through our dry months.

Uh, oh. I neglected to respond to your question about leaf color.

The tree is a Japanese Maple with variegated leaves as are seen on the lower branches. Most likely the all green leaves area a reversion to the "normal" green form. This is not due to a disease.